Do I just have to make a copy of my wallet.dat file?
If referring to bitcoin core then yes, that would be sufficient.
yes, the file with the format
.dat that must be backed up because I also do that. and if you need a copy that is quite a lot in various places then do backups in all places, the most important thing you can keep the data.
handling in managing data becomes an important concern, because the data is your privacy